The truth about tryptophan and Thanksgiving turkey tiredness

Picture yourself at the Thanksgiving table surrounded by relatives and loved ones. Before you is a bountiful table of side dishes and the iconic Thanksgiving turkey. You eat to your heart’s content, reminisce on how long it’s been since you were last together and above all give thanks.

And then: You crash.

An old adage and one particular amino acid puts the turkey as the prime suspect for the post-Thanksgiving dinner crash. But is it true?

“The answer is cut and dry. Eating turkey does not make you sleepy,” said Christopher Smith, Ph.D., MSN, RN, GCQM, assistant professor of nursing who researches cardiometabolic disease and blood pressure dysfunction.

The origin of the myth that turkey is responsible for post-Thanksgiving sleepiness is based on turkey containing tryptophan, an amino acid that converts to serotonin and melatonin, two chemicals associated with sleep regulation. But, turkey doesn’t have significantly more tryptophan than other common foods like chicken, beef, nuts or cheese. On top of that, the other protein and nutrient-rich foods at the table will dilute the effect of tryptophan as their amino acids compete for absorption.

So why do we get so tired after Thanksgiving dinner? Smith named a number of contributing factors: overeating, alcohol consumption and even seasonal factors. But the main cause of drowsiness is the mass consumption of carbohydrates.

Thanksgiving meal staples like stuffing, mashed potatoes, candied yams, rolls and desserts are high on the glycemic index. These foods break down quickly during digestion, causing a rapid rise in blood sugar levels. Initially, you may feel energized. However, the sharp rise in blood sugar is followed by a large release of insulin that may overcompensate to lower your blood sugar.

This dramatic reduction in blood sugar levels can impact cognitive function and lead to feelings of lethargy and sleepiness. At the same time, insulin is a hormone that promotes fat storage and is believed to have a role in regulating leptin, a hormone that signals fullness to the brain and can contribute to feelings of relaxation or tiredness, and ghrelin, a hormone that signals hunger and promotes wakefulness. The large spike in insulin signals these hormones to move in directions that can leave you feeling full, relaxed and amplifies sleepiness.

So, it may not be the turkey, but considering the traditional Thanksgiving spread, is post-meal lethargy inevitable? Smith says that he and his wife eat low-carb during Thanksgiving and anecdotally, he says they can eat a whole turkey without feeling sleepy. But for the average person he recommends conscious eating habits.

“You might try being a bit more mindful about portion sizes and pace yourself while eating,” Smith said. “The faster you eat, the quicker your blood glucose will rise, which can lead to a faster and sharper insulin response.”

Other suggestions Smith provided to combat the negative effects of Thanksgiving dinner include getting light exercise, like a 30-minute walk, and seven to eight hours of quality sleep, which Smith conceded can be hard to come by during the holiday season.

Smith was careful to note the pragmatic difference between what’s in the best interest of people’s health versus the choices we make due to any number of outside influences like the social and cultural pressures of holidays and the impact of dopamine indulgence.

“I think cheating should be approached with a healthy perspective on what cheating means. I wouldn’t encourage anyone to have a gluttonous free-for-all on Thanksgiving. I could never promote that behavior from a health perspective. So, be mindful. Have some awareness. But also, I think people should enjoy the holiday, whatever that means for them.”